Anorexia nervosa is an eating disorder characterized by restrictive eating in which the individuals view themselves as overweight and are afraid of gaining weight even though they are at least 15% below expected weight for age and height. Amenorrhea is a diagnostic criterion for anorexia nervosa.² In this instance, amenorrhea is defined as the lack of three consecutive menstrual cycles. Anorexia nervosa can be further divided into restricting or purging subtypes.

Bulimia nervosa is another eating disorder where the affected individuals are usually in the normal weight range. In Bulimia, individuals repeat a cycle of overeating (binge eating) and then purging. The purging may be from induced vomiting, restricted eating, excessive exercise, misuse of laxatives or medications, or other compensatory behaviors. An individual must have at least two episodes per week for 3 months to meet the criteria for bulimia.

The Diagnostic and Statistical Manual of Mental Diseases, 4th Edition (DSM-IV), outlines the criteria for anorexia nervosa and bulimia nervosa. Athletes who do not meet all the DSM-IV criteria are given the diagnosis of eating disorder not otherwise specified (EDNOS). Disordered eating includes any abnormal eating pattern and is not limited to anorexia nervosa or bulimia. It can include food restriction, fasting, binging, using laxatives, diuretics, and diet pills, or excessive exercise.

Eumenorrhea is defined as a menstrual cycle that lasts 28 days with a standard deviation of 7 days. This is the median interval for young adult women. Oligomenorrhea is defined as having a menstrual cycle occur at intervals longer than 35 days.³ Amenorrhea can consist of either primary or secondary amenorrhea. Primary amenorrhea is defined as the absence of menarche after the athlete has reached 15. Secondary amenorrhea refers to the absence of menses for 3 consecutive months or longer.

With respect to the female athlete triad, there is recognition of a spectrum of bone mineral density (BMD) ranging from optimal bone health to osteoporosis.¹ Osteoporosis is defined as a skeletal disorder characterized by compromised bone strength, predisposing a person to an increased risk of fracture. Osteoporosis is not always caused by accelerated bone mineral loss in adulthood. It can also be due to not accumulating optimal BMD during childhood and adolescence. The World Health Organization (WHO) uses T and Z scores for defining osteoporosis and osteopenia. The T score compares an individual’s BMD to the average adult peak BMD. In the nonathlete population, osteopenia is defined as a T score between −1 and −2.5. Osteoporosis is defined as a T score less than −2.5. With a reduction of BMD of 1 standard deviation, the fracture rate doubles.⁴ The Z score compares an individual’s BMD to age and sex-matched controls. The Z score is a more accurate measure of BMD in athletes, because the evidence has shown that weight-bearing sport athletes have a BMD 5% to 15% higher than nonathletes.⁵ The American
College of Sports Medicine (ACSM) position statement on female athlete triad defines low BMD as a Z score between −1.0 and −2.0. The term “low BMD” is defined as a history of nutritional deficiencies, hypoestrogenism, stress fractures, and other secondary clinical risk fractures for fractures. With respect to the female athlete triad, osteoporosis is defined as a Z score less than −2.0. Low BMD can result from premature bone resorption, impaired bone formation, or both. Deficiencies in calcium, vitamin D, and caloric intake lead to increased bone resorption.

A low energy balance whether or not the athlete has an eating disorder affects both BMD and menstrual function. Athletes at greatest risk are those who are vegetarians, who limit the variety of foods they eat, and who exercise for prolonged periods of time. Animal models have shown that a 30% reduction in caloric intake causes both infertility and skeletal demineralization.¹ Low energy availability disrupts the gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) pulsatility. It also increases the rate of bone resorption and decreases the rate of bone formation.¹